There are frequently various radio-based voice networks and data networks available for mobile communication links. In this context, the radio-based voice networks, that is to say GSM networks, DECT networks and UMTS networks, for example, can also be used for data transmission, as can, conversely, radio-based data networks, that is to say WLAN networks, WiMax networks and Bluetooth networks, for example, can also be used for voice transmission (e.g. VoIP=Voice Over Internet Protocol).
While, in many cases, the same requirement (voice transmission, data transmission etc.) can thus be met in the same or a similar quality using different types of mobile networks and hence using different transmission paths, these transmission paths differ, however, in terms of the costs respectively related to their use, in terms of their bandwidth, the delay times, the reliability (connections being cut off) etc.
To be able to take hold in a specific situation between different transmission paths and their respective related advantages and drawbacks as required, what are known as multimodal mobile communication appliances are frequently used. By way of example, these are PCs which have both Bluetooth and WLAN transmission devices, or else mobile radios (telephones) which selectively support connections based on the GSM standard, the UMTS standard and/or the DECT standard. Before setting up a communication link, for example a telephone call, a user of such a communication appliance can thus select the transmission path which is to be used for the next communication link. Alternatively, it is also possible to permanently preset different transmission paths (GSM, GPRS, DECT) for different communication services (voice, fax, SMS, Internet WWW, etc.).
Frequently, a transmission path is also selected automatically by the communication appliances by checking the availability of the various transmission paths at the time at which a communication link is initiated. To this end, by way of example, a field strength measurement is used to check whether the various base stations of different transmission paths (for example DECT, WLAN) can be received. If it is available, the (inexpensive) WLAN network is then selected, for example, using a priority list, whereas a GSM mobile radio link is selected as the transmission path if a WLAN network or a DECT cell is not available.
The document US 2004/0242240 A1 Lin “Location Assisted Communications Mode Switching” discloses a method in which multimodal terminals take their geographical position as a basis for reading a preferred communication mode from a table and, if the terminal is in another communication mode, changing to this selected communication mode. This process is repeated at regular intervals of time.
The document U.S. Pat. No. 5,752,164 Jones “Autonomous Remote Measurement Unit for Personal Communications Service System” discloses a method for a communication network, in which different frequency channels of a wide frequency band can be used alternately for communication. In this case, the area in which the communication system is used is divided into a number of honeycomb-like regions, with interference on or use of the individual radio channels being measured for each region by means of measuring devices provided in each honeycomb and being stored in a central database. These measurements are preferably taken repeatedly and used to maintain the database formed thereby. When a mobile terminal is used, position-finding is performed for this terminal, and access to the database is used to establish which radio channels are free or have little interference, so that a free or low-interference radio channel can be used for communication.
The document U.S. Pat. No. 5,974,328 Lee et al. “Rapid System Access and Registration in Mobile Phone Systems” likewise discloses a database-based method for location-dependent configuration of a mobile terminal. In this case, a mobile terminal is supplied with respective optimized registration parameters for registration in a mobile radio network from a database on the basis of location.